Plastic and textile materials and methods



Patented Apr. 21, 1953 OFFICE PLASTIC AND TEXTILE MATERIALS AND METHODSOrlan M. Arnold, Grosse Pointe Park, Mich.

N Drawing. Application November 29, 1951, Serial No. 259,009

8 Claims.

This invention relates to plastic compositions in molded and fibrousforms, and to correlated improvements appertaining thereto, and tomethods of making and treating such materials with particular referenceto plastic compositions of the thermoplastic type. This application is acontinuation-in-part of my co-pending application Serial No. 617,433,filed September 19, 1945.

One object of the invention is to improve the oxidation resistance ofnylon and the like polyamide materials. A more specific object is theprovision of ways of economically utilizing waste rayon, waste nylon,etc., etc. Another more specific object is the provision of means forimproving the quality and prolonging the life of fabrics. Another objectis the formation of novel and useful products containing polyamides.Still another object is the provision of an improved plastic for moldingunder heat and pressure. Other objects will in part be obvious and willin part appear more fully hereinafter.

I have discovered that when a synthetic organic fiber-forming linearsuperpolyamide is intimately associated with a cellulosic plasticmaterial, preferably of the thermo-plastic type such as cellulose estersincluding cellulose acetate, cellulose butyrate, and celluloseacetate-butyrate, and cellulose ethers such as ethyl cellulose, and theresulting mixture subjected to heat and pressure as hereinafter moreparticularly described, there is obtained a heatandpressure-consolidated plastic composition that possesses very desirableproperties for manufacturing shaped plastic articles, including threadsand fibers. By the term synthetic organic fiber-forming linearsuperpolyamide as sometimes employed inthis specification, it is to beunderstood that I refer to the class of high molecular weight polymericmaterials exemplified by the commercially available product known asnylon, as developed and manufactured by E. I. du Pont de Nemours 8a(30., of which various species are fully described in numerous du Pontpatents and in the literature of fiber synthesis, including by way ofexample, the patents: Carothers 2,071,250-3, 2,130,948, 2,158,064 and2,190,770. These polymeric materials may also be defined as syntheticlinear polycarbonamides wherein the average number of carbon atoms inthe segments of the chain separating the amide groups is at least two,asin Schupp Patent No. 2,359,877. Textile nylon, with which thisinvention is primarily concerned for utilization of waste, is well knownto be a linear super polymerformed by condensation of hexamethylenediamine and adipic acid and its chemical equivalents, when spun intofilaments and cold-drawn to give fibers with molecular orientationlongitudinal of the fiber axis. Since this component of my compositionis well known and is not per se my invention, further reference theretoi deemed unnecessary in the interests of brevity.

I have found that when nylon is covered or otherwise intimatelyassociated with a film of cellulosic plastic material and especially acellulose ester, desirably cellulose acetate or butyrate, etc., theresulting product is less subject than the nylon alone to deteriorationby oxidation, even at softening temperatures, and that the product is ingeneral more heat-resistant. By combining in this way cellulosic plasticmaterials and the like with nylon, I have discovered that used nylonfabric and other waste nylon materials may be efiiciently utilized inthe production of new compositions, such as plastics and fibers, whichpossess not only the desirable properties of one or both of thecomponents but also other desirable properties which are not found ineither of the components of the composition. For example, the. productobtained by heating waste cellulose acetate and nylon fabric together,with or without mechanical working and fluid pressure, has a higherfusion point than either the cellulose acetate or the nylon alone.

I have good reason to believe that a chemical combination takes placebetween the cellulosic component and the nylon component by whichmolecules of these respective polymeric materials are tied together intolonger chains or supercopolymers. .At the same time adjacent fibers maybe fused together by chemical linkages at points of contact. Howeverwhile there is indeed good reason to believe that a true chemicalcombination takes place, it is nevertheless to be understood that I donot regard myself as bound by any such theory, however plausible, andthat my invention is based upon the association of the materials as andin the manner described hereinafter irrespectively of whether or notchemical combination takes place.

It is only necessary and generally desirable to apply a very thin filmof the organic cellulosic plastic material to the nylon or otherpolyamide fiber or film, but more can be used if desired. I have, forexample, used proportions of the organic cellulosic plastic material,such as cellulose acetate, of from 2% to and more by weight of thenylon, but I have also found that generally speaking the best resultsare obtained when operating in the range of from 2% to 30% based on theweight of the nylon. Furthermore, I have additionally found that from 2%to of the cellulosic component, based on the weight of the nylon in thecomposition, represents the optimum range for best all-around results.

While I have referred to the feature of applying a very thin film orsheath of the cellulosic plastic material to nylon fibers which havebeen.

oriented by stretching, the rocess of the present invention may also bethought of as involving fundamentally the intimate association of the.polymeric molecules of the aforesaid principal. components of thecomposition; but" the use off oriented nylon and dissolution of thecellulose facilitates the coming together of. the'resp'ect'ive.molecules in aspect favorable to the desired cross-linking or bridging.

Although I have not yet been able to prove beyond question what is theprecise nature of.

the reaction of the cellulosic and nylon components under thistreatment; I have observed; that reaction products of thenature hereinset forth are in fact produced; Moreover, such reaction.

is promoted by heating: the components of. the composition totemperatures above about 190-- 225 C.-,and by the applicationof.superatmospheric pressure and/or mechanical working thereto; It has beenfound that to'some-extent the range of temperatures may be: extendeddownward if mechanical working and/or time of heating are increased. Inany case, I. prefer toemploy temperatures in the rangeof fromabout 150C. to as high. as 400 Qdcppendingv upon theexact nature ofthe:components of the composition, the-time of treatmentand the. de.--'

gree of Working; IngeneraL, it: is desirable. to

heat the composition to as'high. a temperature as is feasible,,it beingonlyxessential. inany. given, case to avoid temperatures at whichthecomposie tionwill suffer serious degradation, having. due regard to thetime of exposure ofthe composition to such temperature and to otherconditionsof such exposure including. presence. of oxygen or otherchemically activematerial.

In many" instances, useful products may beformed of. waste nylon andcellulose, celluloseester or cellulose ether fabrics mixed. together. inthe presence of solvents, plasticizers and/or other reactive materials.Desirablyt Whatever such materials are-utilizedshould be of relativelylow: volatility in view of the high: fusion point of the resulting:cellulose-nylon plastic composition. Examples of desirable materials foruseas; iplasticizers forv the polyamide-cellulose acetate:

plastic are triphenyll phosphate, tricresyl' phosphate,. and various.chlorinated diphenyls. such for example as Arochlor No. 1248 or ArochlorNo. 1262 available.fromthaMonsanto Chemical Company. Acetone andetherare effective solvents or vehicles in forming a plastic composition frompolyamide: waste material and cellulose acetate. waste material whereonly temporary softening: is required- Plastic masses; formed bycombiningnylon and. cellulose acetate;

e. g., applied in; acetone solution, can bepulled out like'nylon itselfinto'good strong fibers with advantageous properties. as indicated aboveand likewise can be compressed and molded into hard,

smooth, tough, machinable products of uniform texture. The aforesaidplastic masses. are pref:-

erably formed bymixing nylon fiber and a solution of cellulose acetatein acetone, subjecting.

the mixture to agitation in a suitable. mixing; device. to insureuniform distribution of the cellu-.-- lose acetate. over the'nylonfiber,.and thereafter Y acetate, butyrate, etc. may be preparedindependently-in the-form of a solution in a suitable vehicle and mixedwith waste nylon fabric or fibers, with or without polystyrene. Thecellulose ester (and the polystyrene or styrene monomer, if used) may bedissolved in a suitable solvent, for example acetone, and the resultingsolution mixed withi-or sprayed? upon thefibrous polyamide basematerial.

organic cellulosic plastic material. in. order to thoroughly impregnatesame. with the latter.

The vehicle or. solvent may then beevaporated before-or during the. use.or further-treatmentvof. themixed material;

A- good cellulose ester material= is an acetatebutyratei mixed estersuch. as is employed. for making. fiber-spinning. solutions.

As. one example'of my invention, scrapcellw lose-acetate rayon.- may;bedissolved in-sufficienti acetoneto form a thin, slightly sirupysolution. 'Ihezresultingisolutionis placedin a covered ves.-- s'el.andnylon-yarn; thoroughly cleaned .andfreed: from waxand oils, ispassedcontinuously, through. the solution: as animpregnating bath.The=im-- regnatingfoperation is facilitated by the useof; squeeze rollsimmersed; in the bath and/or by the application of a vacuum to.- theimpregnating: vessel: As the yarn is. withdrawnfromthe bath: itpassesbetween wringer rolls: to remove excess solution and: may then be passedintoadrying chamber where thea-cetone is vaporized offor into a. bath ofpetroleumether, benzene,

carbon tetrachloride or the-like, where the. ace-- toneisleached out,leaving the. cellulose: acetate as a: uniform, finely fibrous depositonthe individual fibers of the: nylon. The impregnated yarn, before orafter removal of the solvent, is

heatedto about'75 C- (e. g., 60 6. for petroleum ether, 7.5 'C. forbenzene, and C. for. carbon tetrachloride), preferably in an-inertatmosphere or" bath, and when. cooled and. dried it. isready for use forweaving; knitting or other textile--pur-- poses.

Instead of cellulose acetate, cellulose butyrate. or butyrate acetate, Imay use; other; cellulosicv plasticmaterials. suchas a cellulose. ether.solu-- tion, e. 55., an alcohol solution of ethyl cellulose,

or the. nylon may be coated. with regenerated.

cellulose by treatingwith a cuprammonium solution ofcellulose or aviscosesolution of cellulose xanthate; and then precipitating the.cellulose:

ontothernylon by leaching. in the usual coagulatingv baths commonlyemployed in the cuprammonium and viscose rayon-industries, respective-1y. In all:such cases,thecoatedpolyamide yarn is advantageouslyheatedaboveabout Gate drive oiT' residual; solvent. The productv ofsuchtreatment may be used for. improved textiles, but. is alsousef-ulformaking the novel plasticor re-' forming, of. fibers according tothe:present in.- vention.

Alternatively, the fibrous polyamide: materialmay: be dip-pedin sucha-solution of the 'Instead'of treating nylon in the form ofyam, I maytreat other textile fabrics, e. g., woven cloth, knitted stockings,newly formed fibers before spinning into yarn, or short fibers releasedfrom scrap or rag by various reclaiming methods well known in the art.Unspun and unwoven materials, such as felt, sliver, bat, etc., may betreated in like manner, as well as even dense, transparent films similarto cellophane.

. Other polymers may, if desired, be combined with the cellulosicplastic materials, such as polymers and copolymers of styrene, othervinyl compounds, butadiene, etc.

In particular, I have found that a product formed from celluloseacetate, nylon and the like polyamides, and styrene (either in themonom'eric or polymeric state or both) has exceptionally advantageousand unexpectedly desirable properties. It is not clear to just whatextent these materials dissolve or otherwise plasticize. one another andto what extent they form addition products or cross-linked superpolymersor otherwise assist in the mutual polymerization of another. There areevidences of each of a number of types of effects includingplasticization, combination, and co-polymerization of the respectivepolymeric components. In any event, the process is highly effective andthe product highly advantageous, and, as indicated above, I do notdesire to be bound to any particular theory of formation.

For example, a high quality plastic composition is produced frompolyamlde material with polystyrene and. cellulose acetate as follows:20 parts by weight of polyamide in the form of waste nylon stockingmaterial, 2 parts by weight of waste rayon material of the celluloseacetate type, and 1 part by weight of white crystalline polystyrene areground together for about 8 to 10 minutes in a Banbury mixer cooled tomaintain a temperature of about 65 C. in the mass during working. Aplasticized mass which can be effectively molded or extruded is producedin this manner. When molded under 150-200 pounds per square inchpressure at approximately 250- 275C there is obtained a heatandpressureconsolidatedmixture of the components in the form of a plasticcomposition which is hard, smooth, light-weight, of low distortion, andof otherwise unique characteristics. When extruded through narroworifices the extrudate may be drawn out rapidly into textile fibers orfilaments. The pulling out or spinning of the nylon-containingcomposition, as well preferably as the initial molding thereof, isperformed in an inert atmosphere, such for example as nitrogen, or aninert liquid, such for example as hot hydrocarbon oils, or with othersutiable precautions againstoxidation of the'nylon. Well oriented fiberscan be obtained by drawing out at high velocity in a cool atmospherefrom a heated mixture. Lower temperatures in the drawing atmosphere canbe utilized to help protect against degradation, but too rapid coolingmay reduce the strength of the final composition, so that it isgenerally more desirable to immerse the drawn or molded plasticcomposition in an inert bath or atmosphere maintained at a desirableaging temperature.

.The treated materials of my invention may be used for molding as wellas for textile uses. Scrap nylon fabric, before or after treatmentaccording to the present invention, can be reduced to short fiber formsuitable for use in plastic molding and can be treated with thecellulose acetate or other cellulosic plastic material in bat orlooseflber form if not previously treated.

As another example of the invention, I dissolve 1 part by weight ofbright acetate rayon' scrap in 45 parts by weight of acetone. Nylonfibers are cut into short lengths, less than about 1.5 inches tosubstantially avoid forming of tangled masses of fiber on mixing. Theacetate solution is then sprayed onto the nylon fiber in a tumbling typemixer, the proportion of dissolved cellulose acetate being about 10% byweight of the nylon fiber. evaporated and the product is dried in amixer where it is fluffed up, e. g., by a paddle. In the final stage ofthe drying a current of air warmed to a little less than 50 C. is passedthrough the material and/ or it is subjected to vacuum.

The dried product is then charged into a Banbury mixer and workedtherein for 10 minutes during which the temperature rises to about 190C.

The proportion of cellulose acetate to nylon may be varied down to about2% and up to about 30%. The temperature can be kept down as low as 150C. if the cellulosic material is suiiiciently plasticized, but forpractical results under commercial conditions 190 C. should be regardedas the lower limit.

Instead of the Banbury mixer one may use other heavy mixers available tothe plastics industry and especially screw-type continuous extrudingplastic mills such as that patented by Gordon.

The product to be sold is a cellulose acetate protected nylon extrudedand cut into pellets of convenient size for use in ordinary moldingoperations. If the mixing has been done in a Banbury or other batchmachine, the product is ad-- vantageously put through a separateextruder and cut into pellets.

The concentration of the cellulosic solution can be varied to suitconvenience, for example I have used a concentration of 1 part celluloseacetate waste fiber to 5 parts acetone.

For molding treated nylon fibers it is often desirable to use pressuresof from to 2000 pounds per square inch or more at temperatures of fromto 300 C. or even as high as 400 C.; lower pressures being used withhigher temperatures longer time and softer material,.an'd lowertemperature for higher pressures, longer. time and softer material, andvice versa.' The time of exposure to the higher temperatures issufficiently short in all cases as to prevent serious heat degradationof the composition. The compositions obtained according to my inventionmay be utilized in molding operations with greater ease and fewerprecautions than nylon. This may be at least in part because one or bothof the other principal components of the. composition satisfy theoxygen-receiving bonds of the nylon, and it may be at least in partbecause theyphysically protect the nylon from oxidation. and it may bedue at least in part to some other action not now fully understood.Nevertheless,

the Banbury mixer (or later in the process) that are in the higher endof the temperature ranges 75', nitrogen.

given herein, reactive agents such as. oxygen the process in The acetoneis then anaemic Instead of heating the treated nylon material at once,it may be merely dried and then woven, felted, spun r compacted in amold and then heated to a temperature near its softening point. Theresult is an exceptionally well-bonded, strong, heat-resistant product.

Also, while I have described my invention with particular reference tonylon fibers coated with organic cellulosic plastic materials, andcompositions comprising such ingredients, in its broader aspects itincludes other fibrous materials and other coating materials wherein aninterreaction occurs forming a super-co-polymer by which the coatingbecomes integrally fused into the modified fiber.

While I have frequently used the terms nylon and synthetic organicfiber-forming linear superpolyamide, as a matter if fact I have obtainedbest results with the utilization of waste nylon from commercialsources, which nylon is substantially water insoluble and fusible, andwhich I understand to be a condensation polymer of hexamethylene diamineand adipic acid manufactured by a process that includes colddrawingfilaments of said polymer into fibers exhibiting by X-ray examinationmolecular orientation along the fiber axis and it is to be understoodthat I regard such materials as most advantageous for use in practicingmy invention; other nylon may also be similarly employed with some ofthe advantages of the invention. v

When the nylon is employed in fibrous form, it is generally convenientto subdivide it into short lengths of fiber for intimate admixture withthe organic cellulosic plastic material. However, it is possible toemploy non-fibrous nylon in practicing the present invention, providedit is subdivided to present a high surface/ volume ratio, therebyinsuring intimate contact between the solution of the organic cellulosicplastic material and the subdivided nylon particles, which therebyreceive a uniform coating of the cellulosic solution which, uponapplication of heat and pressure, is converted into a sheath or filmsurrounding and protecting the subdivided nylon and together with thelatter forming a heatand pressure-consolidated mixture having thedesired properties according to the present invention.

The organic cellulosic plastic materialand the nylon may be separatelypreheated prior to admixture and then subjected to further heat andpressure in a mold to bring about the formation of the desired finalproduct, or these components may be admixed directly in the moldprovided the mold is equipped with agitating means in order to bringabout an intimate mixture of the components, and thereafter immediatelysubjected to heat and pressure in order -to bring about the productionof the desired.

This mixture is then heated-to about 190-225 fabrication operations.

The foregoing procedure is repeated but this time employing thecellulose acetate solution in' an amount sufficient to provide 5%cellulose acetate in the composition based on the weight of nylon. Thefinal'molded product possessed similarly desirable properties, both asregards toughness and machinability and as regards its ability to bespun into useful textile fibers.

Although I have given above certain specific examples of my inventionand its application in practical use and. am giving also certainmodifications and alternatives, it should be understood that these arenot intended to be exhaustive or to be limiting of the invention. On thecontrary I am giving these as illustrations and am giving explanationsherein in order to acquaint others skilled in the art with my inventionand the principles thereof and a suitable manner of its application inpractical use, so that others skilled in the art may be enabled tomodify the invention and to adapt it and apply it in numerous forms,each as may be best suited to the requirements of a particular use.

I claim;

1. A process of manufacturing a hard, tough, plastic composition from apreshaped synthetic organic film-forming linear polycarbonamide whereinthe average number of carbon atoms in the segments of the chainseparating the amide groups is at least two and a cellulosic materialselected from the class consisting of cellulose ethers, cellulose estersand regenerated cellulose, comprising intimately admixing said preshapedpolycarbonamide in finely divided form with from 2 to 60% by weightthereof of said cellulosic material, and consolidating said mixture intosaid hard, tough, plastic composition by subjecting said mixture topressure and elevated temperatures of at least about C.

2. -A process as defined in claim 1 wherein the cellulosic material isemployed in the range of from 2 to 30% by weight of the preshapedpolycarbonamide.

3. A process as defined in claim 1 wherein the cellulosic material isemployed in the range of from 2 to 10% by weight of the preshapedpolycarbonamide.

4.. A process of manufacturing a tough, plastic composition from apreshaped synthetic organic film-forming linear polycarbonamide whereinthe average number of carbon atoms in the segments of the chainseparating the amide groups is at least two and a cellulosic materialselected from the class consisting of cellulose ethers, cellulose estersand regenerated cellulose, comprising intimately admixing said preshapedpolycarbonamide in finely divided form with from 2 to'30% by weightthereof of said cellulosic material, initially mixing at a temperaturebelow 100 C., heating the mixture to a temperature of at least 150 0.,and thereafter consolidating said mixture into said tough, plasticcomposition by applying heat and pressure to the mixture.

5. A process of manufacturing a tough, plastic composition from apreshaped synthetic organic film-forming linear polycarbonamide whereinthe average number of carbon atoms in the segments of the chainseparating the amide groups is at least two and a cellulosic materialselected from the class consisting of cellulose ethers, cellulose estersand regenerated cellulose, comprising intimately admixing said preshapedpolycarbonamide 'in finely divided form with from 2 to 30% by weightthereof of said cellulosic material, initially heating the mixture to atemperature of at least 150 C., and thereafter consolidating saidmixture into said tough, plastic composition by heating said mixture atpressures of at least 100 pounds per square inch at temperatures of atleast 90 C.

6. A process as defined in claim 5 wherein the cellulosic material isemployed in the range of 10 from 2 to 10% by weight of the preshapedpolycarbonamide.

7. A process as defined in claim 1 wherein said preshapedpolycarbonamide consists essentially of waste from commercial sources.

8. A process as defined in claim 1 wherein said preshapedpolycarbonamide is a condensation polymer of hexamethylene diamine andadipic acid manufactured by a process that includes cold-drawingfilaments of said polycarbonamide into fibers exhibiting by X-rayexamination molecular orientation along the fiber axis.

ORLAN M. ARNOLD.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 30 2,190,770 Carothers Feb. 20', 1940 2,285,178 Thinius June2, 1942 2,347,525 Thinius Apr. 25, 1944: 8,416,890 Amende et al. Mar. 4,1947

1. A PROCESS OF MANUFACTURING A HARD, TOUGH, PLASTIC COMPOSITION FROM APRESHAPED SYNTHETIC ORGANIC FILM-FORMING LINEAR POLYCARBONAMIDE WHEREINTHE AVERAGE NUMBER OF CARBON ATOMS IN THE SEGMENTS OF THE CHAINSEPARATING THE AMIDE GROUPS IS AT LEAST TWO AND A CELLULOSIC MATERIALSELECTED FROM THE CLASS CONSISTING OF CELLULOSE ETHERS, CELLULOS ESTERSAND REGENERATED CELLULOSE, COMPRISING INTIMATELY ADMIXING SAID PRESHAPEDPOLYCARBONAMIDE IN FINELY DIVIDED FORM WITH FROM 2 TO 60% BY WEIGHTTHEREOF OF SAID CELLULOSIC MATERIAL, AND CONSOLIDATING SAID MIXTURE INTOSAID HARD, TOUGH, PLASTIC COMPOSITION BY SUBJECTING SAID MIXTURE TOPRESSURE AND ELEVATED TEMPERATURES OF AT LEAST ABOUT 100* C.